OpenAPIExtensions

SDK variables

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The x-fern-sdk-variables extension allows you to define variables that are set once during SDK client initialization and automatically used in path parameters across all endpoint calls. This is useful for common parameters like tenant IDs, organization IDs, or environment identifiers that appear in many endpoint paths.

SDK variables are supported in TypeScript (v2.6.3+), Python (v4.24.0+), and Java (v3.6.3+). Only string types are supported.

Configuration

Define variables at the document level using x-fern-sdk-variables, then mark path parameters as variables using x-fern-sdk-variable:

openapi.yml
1x-fern-sdk-variables:
2  gardenId:
3    type: string
4    description: The unique identifier for your garden
5  zoneId:
6    type: string
7    description: The zone within the garden
8
9paths:
10  /gardens/{gardenId}/zones/{zoneId}/plants:
11    get:
12      operationId: list_plants_in_zone
13      parameters:
14        - name: gardenId
15          in: path
16          required: true
17          x-fern-sdk-variable: gardenId
18          schema:
19            type: string
20        - name: zoneId
21          in: path
22          required: true
23          x-fern-sdk-variable: zoneId
24          schema:
25            type: string

SDK usage

Variables become required constructor parameters instead of being passed to individual method calls:

1const client = new PlantClient({
2  gardenId: "garden_123",
3  zoneId: "zone_456",
4  apiKey: "your-api-key"
5});
6
7const plants = await client.listPlantsInZone();